Buttress and surgical stapling apparatus

ABSTRACT

Multilayer structures including a porous layer and a non-porous layer are useful as buttresses when associated with a surgical stapling apparatus.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/274,521, filed Oct. 17, 2011, which is a divisional of U.S.application Ser. No. 11/823,340 filed Jun. 27, 2007, now U.S. Pat. No.8,062,330, the entire disclosures of each of the above-identifiedapplications are hereby incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to surgical buttresses which can bereleasably attached to a surgical stapling apparatus. The buttressescontain a porous layer and a non-porous layer.

2. Background of Related Art

Surgical stapling devices have found widespread application in surgicaloperations where body tissue must be joined or removed. When operatingon certain tissue, such as lung, esophageal, intestinal, duodenal, andvascular tissue, it is important to effectively seal the tissue whichcan be particularly prone to air or fluid leakage. Preventing orreducing air or fluid leakage can significantly decrease post operativerecovery time. Thus, it would be advantageous to provide a material foruse with a surgical stapling device which enhances sealing at thesurgical wound site.

SUMMARY

Buttresses having a porous layer and a non-porous layer are describedherein. The multilayer buttresses are suitable for use in connectionwith a surgical stapling apparatus and assist in the sealing of tissueto prevent the leakage of fluids and gases. The surgical staplingapparatus includes a staple cartridge having a surface with at least oneopening through which a staple may be ejected. The surgical staplingapparatus further includes an anvil having a surface against which anejected staple may be deformed. A buttress in accordance with thepresent disclosure may be associated with either the staple cartridge,the anvil, or both.

In embodiments, the porous layer possesses haemostatic properties. Inembodiments, the non-porous layer has anti-adhesion properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one illustrative embodiment of a linearsurgical stapling apparatus.

FIG. 2A is a perspective view of a staple cartridge that includes amultilayer buttress in accordance with the present disclosure.

FIG. 2B is a perspective view of a staple anvil that includes amultilayer buttress in accordance with the present disclosure.

FIG. 3A is a side view of a multilayer buttress as described in oneembodiment herein.

FIG. 3B is a side view of a multilayer buttress as described in oneembodiment herein.

FIG. 3C shows an illustrative embodiment wherein fibers present in morethan one layer are used as the reinforcement member, with the fibers inone layer being oriented in a first common direction and the fibers inthe other layer being oriented in a second common direction that issubstantially perpendicular to the first common direction.

FIG. 3D shows an illustrative embodiment wherein chopped fibers are usedas the reinforcement member.

FIG. 4 is a perspective view of a staple cartridge that includes amultilayer buttress releasably attached thereto.

FIG. 5A schematically shows a porous layer wherein the pores or openingsextend across the entire thickness thereof in accordance withembodiments of the present disclosure.

FIG. 5B schematically shows a porous layer wherein the pores or openingsdo not extend across the entire thickness thereof in accordance withembodiments of the present disclosure.

FIG. 5C schematically shows a porous layer wherein the pores or openingsare present on only a portion of the surface thereof in accordance withembodiments of the present disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the presently disclosed multilayer buttress and surgicalstapling apparatus will now be described in detail with reference to thedrawing figures wherein like reference numerals identify similar oridentical elements.

The multilayer surgical buttress described herein may be used in sealinga wound by approximating the edges of wound tissue between the staplecartridge and the staple anvil of a stapling apparatus which contains atleast one multilayer surgical buttress having a non-porous layer and aporous layer and firing the stapling apparatus to force at least onestaple to pass through the openings on the staple cartridge, at leastone multilayer buttress, the tissue and the openings on the staple anvilto seal the tissue. Once stapled in place the porous layeradvantageously reduces bleeding, assists in sealing the wound andallowing tissue ingrowth, if desired, while the non-porous layerprovides support for the porous layer and may assist in preventing theformation of adhesions. In addition, the multilayer buttress mayoptionally include an additional reinforcement member (which, asdescribed in more detailed below, may be absorbable or non-absorbable)to provide additional support to the multilayer buttress and assist inpreventing tears during stapling.

It should be understood that buttresses need not be associated with boththe staple cartridge and the anvil. Rather, a buttress may be associatedwith only the staple cartridge and not the anvil or with the anvil andnot the staple cartridge. In addition, the multilayer surgical buttressdescribed herein may be configured into any shape, size or dimensionsuitable to fit any surgical stapling, fastening or firing apparatus.Other examples of stapling apparatus which may utilize the multilayerbuttress material described herein includes laparoscopic staplers (see,e.g., U.S. Pat. Nos. 6,330,965 and 6,241,139, the entire contents ofwhich are incorporated herein by this reference), alternative staplingapparatus of the transverse anastomosis type for stapling a patient'smesentery (see, e.g., U.S. Pat. No. 5,964,394, the entire content ofwhich is incorporated herein by this reference), and end-to-endanastomosis types for performing surgical anastomotic stapling with acircular cartridge and anvil mesentery (see, e.g., U.S. Pat. No.5,915,616, the entire content of which is incorporated herein by thisreference). The present buttresses may also be used in conjunction withinstruments that apply two-part fasteners wherein a first part of thetwo-part fastener is stored in a cartridge or like member and can befired and properly joined to a second part of the two-part fastenerdisposed in an anvil or like member. Those skilled in the art havingread the present disclosure will readily envision how to adapt thepresent buttresses for use in connection with such apparatus and alsoenvision other surgical apparatus with which the buttresses describedherein may be used.

Now turning to FIGS. 3A and 3B, buttress 350 is shown having anon-porous layer 360 and a porous layer 370. It is envisioned thatbuttress 350 may contain a plurality of layers in which any combinationof non-porous and porous layers may be configured. For example, amultilayer buttress may be formed in which multiple non-porous layersand porous layers are stacked in an alternating manner. In anotherexample, the multilayer buttress may be formed in a “sandwich-like”manner wherein the outer layers of the multilayer buttress includeporous layers and the inner layers are non-porous layers. It is furtherenvisioned that the non-porous layer and porous layer may be positionedin any order relative to the surfaces of staple cartridge and stapleanvil.

The non-porous layer of the buttress may be made from any biocompatiblematerial. Thus, the non-porous layer of the multilayer buttressdescribed herein may be formed from a natural material or a syntheticmaterial. The material from which the non-porous layer is formed may bebioabsorbable or non-bioabsorbable. It should of course be understoodthat any combination of natural, synthetic, bioabsorbable andnon-bioabsorbable materials may be used to form the non-porous layer.Some non-limiting examples of materials from which the non-porous layermay be made include but are not limited to poly(lactic acid), poly(glycolic acid), poly (hydroxybutyrate), poly (phosphazine), polyesters,polyethylene glycols, polyethylene oxides, polyacrylamides,polyhydroxyethylmethylacrylate, polyvinylpyrrolidone, polyvinylalcohols, polyacrylic acid, polyacetate, polycaprolactone,polypropylene, aliphatic polyesters, glycerols, poly(amino acids),copoly (ether-esters), polyalkylene oxalates, polyamides, poly(iminocarbonates), polyalkylene oxalates, polyoxaesters,polyorthoesters, polyphosphazenes and copolymers, block copolymers,homopolymers, blends and combinations thereof.

In embodiments, natural biological polymers are used in forming thenon-porous layer of the buttress. Suitable natural biological polymersinclude, but are not limited to, collagen, gelatin, fibrin, fibrinogen,elastin, keratin, albumin, hydroxyethyl cellulose, cellulose, oxidizedcellulose, hydroxypropyl cellulose, carboxyethyl cellulose,carboxymethyl cellulose, chitan, chitosan, and combinations thereof. Inaddition, the natural biological polymers may be combined with any ofthe other polymeric materials described herein to produce the supportlayer of the buttress.

In embodiments, collagen of human and/or animal origin, e.g., type Iporcine or bovine collagen, type I human collagen or type III humancollagen, may be used to form the non-porous layer.

Native collagen may advantageously be used in acid solution or afterprocessing, to eliminate the telopetpides, notably by pepsin digestion.The collagen, e.g., atelocollagen, can also be modified by oxidativecleavage by the use of periodic acid or one of its salts. The oxidativecleavage of the collagen allows for future moderate crosslinking in thecollagenic material with other polymeric materials, macromolecularadditives or the haemostatic agents contained in the haemostatic layerof the buttress.

In embodiments, the non-porous layer according to the present disclosureis made of collagen which is oxidized or a mixture in any proportions ofnon-oxidized and oxidized collagens.

In embodiments, at least one macromolecular additive may be combinedwith the collagen to provide a composition from which the non-porouslayer is formed. Some examples of suitable macromolecular additivesinclude, polyethylene glycol, glycerin, polysaccharides, dextran,maltodextrin, mucopolysaccharides, cellulose, alginate and combinationsthereof. When used, the macromolecular additive may have a molecularweight of at least 3,000 Daltons and may represent a concentration fromabout 2 to 10 times less than the collagenic material present in thecomposition from which the non-porous layer is formed.

The non-porous layer may enhance the ability of the buttress to resisttears and perforations during the manufacturing, shipping, handling andstapling processes. Also, the non-porous layer may also retard orprevent tissue ingrowth from surrounding tissues thereby acting as anadhesion barrier and preventing the formation of unwanted scar tissue.Thus, in embodiments, the non-porous layer possesses anti-adhesionproperties.

It is envisioned that the buttress may be releasably attached to thecartridge and/or the anvil in any manner capable of retaining thebuttress in contact with the cartridge and/or the anvil prior to andduring the stapling process, while allowing the buttress to be removedor released from the cartridge and/or the anvil following thepenetration of the buttress by a surgical staple or other fasteningdevice. For example, the buttress may be attached to the cartridgeand/or the anvil using adhesives, sealants, glues, pins, tacks, tabs,clamps, channels, straps, protrusions and combinations thereof.

The non-porous layer may be formed using techniques within the purviewof those skilled in the art, such as casting, molding and the like.

The porous layer of the buttress has openings or pores over at least aportion of a surface thereof. As described in more detail below,suitable materials for forming the porous layer include, but are notlimited to fibrous structures (e.g., knitted structures, wovenstructures, non-woven structures, etc.) and/or foams (e.g., open orclosed cell foams). In embodiments, the pores may be in sufficientnumber and size so as to interconnect across the entire thickness of theporous layer. Woven fabrics, kitted fabrics and open cell foam areillustrative examples of structures in which the pores can be insufficient number and size so as to interconnect across the entirethickness of the porous layer. In embodiments, the pores do notinterconnect across the entire thickness of the porous layer. Closedcell foam or fused non-woven materials are illustrative examples ofstructures in which the pores may not interconnect across the entirethickness of the porous layer. FIG. 5A schematically illustrates a foamporous layer wherein the pores span across the entire thickness ofporous layer. In yet other embodiments, the pores do not extend acrossthe entire thickness of the porous layer, but rather are present at aportion of the surface thereof. FIG. 5B schematically illustrates aporous layer wherein the pores do not span across the entire thicknessthereof. In embodiments, the openings or pores are located on a portionof the surface of the porous layer, with other portions of the porouslayer having a non-porous texture. FIG. 5C schematically illustrates aporous layer wherein the pores do not cover the entire surface of theporous layer, but rather are present on a central portion thereof. Thoseskilled in the art reading the present disclosure will envision otherpore distribution patterns and configurations for the porous layer.

Where the porous layer is fibrous, the fibers may be filaments orthreads suitable for knitting or weaving or may be staple fibers, suchas those frequently used for preparing non-woven materials. The fibersmay be made from any biocompatible material. Thus, the fibers may beformed from a natural material or a synthetic material. The materialfrom which the fibers are formed may be bioabsorbable ornon-bioabsorbable. It should of course be understood that anycombination of natural, synthetic, bioabsorbable and non-bioabsorbablematerials may be used to form the fibers. Some non-limiting examples ofmaterials from which the fibers may be made include, but are not limitedto poly(lactic acid), poly (glycolic acid), poly (hydroxybutyrate), poly(phosphazine), polyesters, polyethylene glycols, polyethylene oxides,polyacrylamides, polyhydroxyethylmethylacrylate, polyvinylpyrrolidone,polyvinyl alcohols, polyacrylic acid, polyacetate, polycaprolactone,polypropylene, aliphatic polyesters, glycerols, poly(amino acids),copoly (ether-esters), polyalkylene oxalates, polyamides, poly(iminocarbonates), polyalkylene oxalates, polyoxaesters,polyorthoesters, polyphosphazenes and copolymers, block copolymers,homopolymers, blends and combinations thereof.

Where the porous layer is fibrous, the porous layer may be formed usingany method suitable to forming fibrous structures, including but notlimited to knitting, weaving, non-woven techniques and the like.Suitable techniques for making fibrous structures are within the purviewof those skilled in the art.

Where the porous layer is a foam, the porous layer may be formed usingany method suitable to forming a foam or sponge including, but notlimited to the lyophilization or freeze-drying of a composition.Suitable techniques for making foams are within the purview of thoseskilled in the art.

In embodiments, the porous layer possesses haemostatic properties.Illustrative examples of materials which may be used in providing theporous layer with the capacity to assist in stopping bleeding orhemorrhage include, but are not limited to, poly(lactic acid),poly(glycolic acid), poly(hydroxybutyrate), poly(caprolactone),poly(dioxanone), polyalkyleneoxides, copoly(ether-esters), collagen,gelatin, thrombin, fibrin, fibrinogen, fibronectin, elastin, albumin,hemoglobin, ovalbumin, polysaccharides, hyaluronic acid, chondroitinsulfate, hydroxyethyl starch, hydroxyethyl cellulose, cellulose,oxidized cellulose, hydroxypropyl cellulose, carboxyethyl cellulose,carboxymethyl cellulose, chitan, chitosan, agarose, maltose,maltodextrin, alginate, clotting factors, methacrylate, polyurethanes,cyanoacrylates, platelet agonists, vasoconstrictors, alum, calcium, RGDpeptides, proteins, protamine sulfate, epsilon amino caproic acid,ferric sulfate, ferric subsulfates, ferric chloride, zinc, zincchloride, aluminum chloride, aluminum sulfates, aluminum acetates,permanganates, tannins, bone wax, polyethylene glycols, fucans andcombinations thereof.

Generally, the use of natural biological polymers, and in particularproteins, is particularly useful in forming porous layers havinghaemostatic properties. Suitable natural biological polymers include,but are not limited to, collagen, gelatin, fibrin, fibrinogen, elastin,keratin, albumin and combinations thereof. In such embodiments, thenatural biological polymers may be combined with any other haemostaticagent to produce the porous layer of the buttress. The origin and typesof collagens that may be used to form the porous layer are the same asthose indicated above for the non-porous layer. However, the oxidized ornon-oxidized collagen may be lyophilized, freeze-dried, or emulsified inthe presence of a volume of air to create a foam and then freeze-dried,to form a porous compress.

In embodiments, the porous layer may be made from denatured collagen orcollagen which has at least partially lost its helical structure throughheating or any other method, consisting mainly of non-hydrated α chains,of molecular weight close to 100 kDa. The term “denatured collagen”means collagen which has lost its helical structure. The collagen usedfor the porous layer as described herein may be native collagen oratellocollagen, notably as obtained through pepsin digestion and/orafter moderate heating as defined previously. The collagen may have beenpreviously chemically modified by oxidation, methylation, succinylation,ethylation or any other known process.

In embodiments, the porous layer can be obtained by freeze-drying anaqueous acid solution or suspension of collagen at a concentration ofabout 2 to about 50 g/l and at an initial temperature of about 4 toabout 25° C. The concentration of collagen in the solution can be fromabout 1 g/l to about 30 g/l and in embodiments about 10 g/l. Thissolution is advantageously neutralized to a pH of about 6 to about 8.

In embodiments, the porous layer can be at least 0.1 cm thick. Inembodiments the thickness of the porous layer can range from about 0.2to about 1.5 cm thick. The porous layer can have a density of not morethan about 75 mg collagen/cm² and in embodiments below about 7 mgcollagen/cm². The size of the pores in the porous layer can be fromabout 20 μm to about 200 μm, in embodiments from about 100 μm to about200 μm.

The haemostatic agents from which the porous layer can be made or whichcan be included in the porous layer can be in the form of foams, fibers,filaments, meshes, woven and non-woven webs, compresses, pads, powders,flakes, particles and combinations thereof. In embodiments, the porouslayer having haemostatic properties provides to the multilayer buttresswhen hydrated characteristics similar to that of the tissue to which thebuttress is applied.

The multilayer buttress material described herein may be formed usingany method known to those skilled in the art capable of connecting anon-porous layer to a porous layer. It is envisioned that the non-porouslayer and the porous layer may be adhered to one another using chemicalbonding, surgical adhesives, surgical sealants, and surgical glues. Inaddition, the layers may be bound together using mechanic means such aspins, rods, screws, clips, etc. Still further, the layers may naturallyor through chemical or photoinitiation may interact and crosslink orprovide covalent bonding between the layers.

In embodiments, the multilayer buttress described herein is prepared byattaching the individual layers of materials together to form a multiplelayer buttress. The porous layer may be formed separate and apart fromthe non-porous layer. Alternatively, the porous and non-porous layersmay be formed together.

In some embodiments, the porous layer may be attached to the non-porouslayer, in a manner which allows the two layers to crosslink and form achemical bond creating a multilayer buttress material capable of sealingtissue. One such example includes pouring a solution of the materialfrom which the non-porous layer is to be made into a mold and applyingthe porous layer to the poured solution during the gelification process.As described in U.S. Pat. No. 6,596,304, which the entire content ofwhich is incorporated herein by reference, the porous layer may containa porous compress made from collagen. The non-porous layer may be madefrom a biopolymer film containing collagen, polyethylene and glycerol.The porous layer may be added to the non-porous film and allowed tocrosslink to form multilayer material suitable for reinforcing a stapleor suture line.

As further shown in FIGS. 3A and 3B, buttress 350 may also include areinforcement member 380. In FIG. 3A, reinforcement member 380 is shownbeing positioned between non-porous layer 360 and porous layer 370 ofbuttress 350 and in FIG. 3B, reinforcement member 380 is shown beingpositioned solely within an individual layer, supporting in this casenon-porous layer 360 of buttress 350. It is envisioned thatreinforcement member 380 may also be positioned within the porous layer.The reinforcement member may also be positioned at the surface of one ofthe layers making up the multilayer buttress and, in embodiments, may bepositioned at an exterior surface of the multilayer buttress.

Some suitable non-limiting examples of the reinforcement member includemeshes, monofilaments, multifilament braids, chopped fibers (sometimesreferred to in the art as staple fibers) and combinations thereof.

Where the reinforcement member is a mesh, it may be prepared using anytechnique known to those skilled in the art, such as knitting, weaving,tatting, knipling or the like.

Where monofilaments or multifilament braids are used as thereinforcement member, the monofilaments or multifilament braids may beoriented in any desired manner. For example, the monofilaments ormultifilament braids may be randomly positioned with respect to eachother within the buttress structure. As another example, themonofilaments or multifilament braids may be oriented in a commondirection within the buttress. In embodiments, monofilaments ormultifilament braids are associated with both the porous layer and withthe non-porous layer. In an illustrative embodiment of this type shownin FIG. 3C, buttress 350 includes a first reinforcement member 381having a plurality of reinforcement members oriented in a firstdirection within the non-porous layer 360 and a second reinforcementlayer 382 having a plurality of reinforcement members oriented in asecond direction within the porous layer 370. In embodiments, the firstand second directions may be substantially perpendicular to each otheras seen in FIG. 3C.

Where chopped fibers are used as the reinforcement member, the choppedfibers may be oriented in any desired manner. For example, the choppedfibers may be randomly oriented or may be oriented in a commondirection. The chopped fibers can thus form a non-woven material, suchas a mat or a felt. The chopped fibers may be joined together (e.g., byheat fusing) or they may be unattached to each other. The chopped fibersmay be of any suitable length. For example, the chopped fibers may befrom 0.1 mm to 100 mm in length, in embodiments, 0.4 mm to 50 mm inlength. FIG. 3D shows an illustrative embodiment wherein buttress 350has chopped fibers 380 incorporated in first non-porous layer 360 a andin second non-porous layer 360 b which can be applied to opposing sidesof porous layer 370.

It is envisioned that the reinforcement member may be formed from anybioabsorbable, non-bioabsorbable, natural, and synthetic materialpreviously described herein including derivatives, salts andcombinations thereof. In particularly useful embodiments, thereinforcement member may be made from a non-bioabsorbable material toprovide long term flexible tissue support. In embodiments, thereinforcement member is a surgical mesh made from polypropylene orpolylactic acid. In addition polyethylene materials may also beincorporated into the buttress described herein to add stiffness. Wheremonofilaments or multifilament braids are used as the reinforcementmember, any commercially available suture material may advantageously beemployed as the reinforcement member.

Turning now to FIG. 4, one embodiment is shown in which multilayerbuttress 350 includes at least one hole 390 which is shaped and designedto frictionally fit onto at least one pin 400 located on staplecartridge 104 and/or staple anvil 204. Hole 390 and pin 400 are designedto releasably attach multilayer buttress 350 to staple cartridge 104and/or staple anvil 204 and both can be of any size, shape or dimension.

In some embodiments, at least one bioactive agent may be combined withthe buttress material and/or any of the individual components (theporous layer, the non-porous layer and/or the reinforcement member) usedto construct the buttress material. In these embodiments, the buttressmaterial can also serve as a vehicle for delivery of the bioactiveagent. The term “bioactive agent”, as used herein, is used in itsbroadest sense and includes any substance or mixture of substances thathave clinical use. Consequently, bioactive agents may or may not havepharmacological activity per se, e.g., a dye, or fragrance.Alternatively a bioactive agent could be any agent which provides atherapeutic or prophylactic effect, a compound that affects orparticipates in tissue growth, cell growth, cell differentiation, ananti-adhesive compound, a compound that may be able to invoke abiological action such as an immune response, or could play any otherrole in one or more biological processes. It is envisioned that thebioactive agent may be applied to the medial device in any suitable formof matter, e.g., films, powders, liquids, gels and the like.

Examples of classes of bioactive agents which may be utilized inaccordance with the present disclosure include anti-adhesives,antimicrobials, analgesics, antipyretics, anesthetics, antiepileptics,antihistamines, anti-inflammatories, cardiovascular drugs, diagnosticagents, sympathomimetics, cholinomimetics, antimuscarinics,antispasmodics, hormones, growth factors, muscle relaxants, adrenergicneuron blockers, antineoplastics, immunogenic agents,immunosuppressants, gastrointestinal drugs, diuretics, steroids, lipids,lipopolysaccharides, polysaccharides, and enzymes. It is also intendedthat combinations of bioactive agents may be used.

Anti-adhesive agents can be used to prevent adhesions from formingbetween the implantable medical device and the surrounding tissuesopposite the target tissue. In addition, anti-adhesive agents may beused to prevent adhesions from forming between the coated implantablemedical device and the packaging material. Some examples of these agentsinclude, but are not limited to poly(vinyl pyrrolidone), carboxymethylcellulose, hyaluronic acid, polyethylene oxide, poly vinyl alcohols andcombinations thereof.

Suitable antimicrobial agents which may be included as a bioactive agentin the bioactive coating of the present disclosure include triclosan,also known as 2,4,4′-trichloro-2′-hydroxydiphenyl ether, chlorhexidineand its salts, including chlorhexidine acetate, chlorhexidine gluconate,chlorhexidine hydrochloride, and chlorhexidine sulfate, silver and itssalts, including silver acetate, silver benzoate, silver carbonate,silver citrate, silver iodate, silver iodide, silver lactate, silverlaurate, silver nitrate, silver oxide, silver palmitate, silver protein,and silver sulfadiazine, polymyxin, tetracycline, aminoglycosides, suchas tobramycin and gentamicin, rifampicin, bacitracin, neomycin,chloramphenicol, miconazole, quinolones such as oxolinic acid,norfloxacin, nalidixic acid, pefloxacin, enoxacin and ciprofloxacin,penicillins such as oxacillin and pipracil, nonoxynol 9, fusidic acid,cephalosporins, and combinations thereof. In addition, antimicrobialproteins and peptides such as bovine lactoferrin, lactoferricin B andantimicrobial polysaccharides such as fucans and derivatives may beincluded as a bioactive agent in the bioactive coating of the presentdisclosure.

Other bioactive agents which may be included as a bioactive agent in thecoating composition applied in accordance with the present disclosureinclude: local anesthetics; non-steroidal antifertility agents;parasympathomimetic agents; psychotherapeutic agents; tranquilizers;decongestants; sedative hypnotics; steroids; sulfonamides;sympathomimetic agents; vaccines; vitamins; antimalarials; anti-migraineagents; anti-parkinson agents such as L-dopa; anti-spasmodics;anticholinergic agents (e.g. oxybutynin); antitussives; bronchodilators;cardiovascular agents such as coronary vasodilators and nitroglycerin;alkaloids; analgesics; narcotics such as codeine, dihydrocodeinone,meperidine, morphine and the like; non-narcotics such as salicylates,aspirin, acetaminophen, d-propoxyphene and the like; opioid receptorantagonists, such as naltrexone and naloxone; anti-cancer agents;anti-convulsants; anti-emetics; antihistamines; anti-inflammatory agentssuch as hormonal agents, hydrocortisone, prednisolone, prednisone,non-hormonal agents, allopurinol, indomethacin, phenylbutazone and thelike; prostaglandins and cytotoxic drugs; estrogens; antibacterials;antibiotics; anti-fungals; anti-virals; anticoagulants; anticonvulsants;antidepressants; antihistamines; and immunological agents.

Other examples of suitable bioactive agents which may be included in thecoating composition include viruses and cells, peptides, polypeptidesand proteins, analogs, muteins, and active fragments thereof, such asimmunoglobulins, antibodies, cytokines (e.g. lymphokines, monokines,chemokines), blood clotting factors, hemopoietic factors, interleukins(IL-2, IL-3, IL-4, IL-6), interferons (β-IFN, (α-IFN and γ-IFN),erythropoietin, nucleases, tumor necrosis factor, colony stimulatingfactors (e.g., GCSF, GM-CSF, MCSF), insulin, anti-tumor agents and tumorsuppressors, blood proteins, gonadotropins (e.g., FSH, LH, CG, etc.),hormones and hormone analogs (e.g., growth hormone), vaccines (e.g.,tumoral, bacterial and viral antigens); somatostatin; antigens; bloodcoagulation factors; growth factors (e.g., nerve growth factor,insulin-like growth factor); protein inhibitors, protein antagonists,and protein agonists; nucleic acids, such as antisense molecules, DNAand RNA; oligonucleotides; polynucleotides; and ribozymes.

EXAMPLE 1 Preparation of Porous Layer

Type I porcine collagen is extracted from pig dermis and renderedsoluble through pepsin digestion and purified by saline precipitation.

A 10 g/l solution of the collagen is prepared by dissolving 23 g of dampcollagen (12% humidity) in 2070 g of ultrafiltered water, at an ambienttemperature below 25° C. It is neutralized using sodium hydroxide to aneutral pH, which leads to precipitation of the collagen.

A porous layer suitable for use in making a multilayer buttress isprepared by poring the suspension onto freeze-dry plates, with 0.5 to 1g/cm² and freeze-drying, using one cycle lasting about 24 hours.

Optionally, in a variant, the freeze-dried porous layer so produced canbe heated to 60° C. for several hours (4 to 15), which provides it withbetter cohesion and mechanical resistance in certain applications.

Preparation of a Solution of Oxidized Collagen Used to Form a Non-PorousFilm

Type I porcine collagen is extracted from pig dermis and renderedsoluble through pepsin digestion and purified by saline precipitation.

A 30 g/l solution of oxidized collagen used for this example, isprepared according to patent FR-A-2 715 309.

Dry collagen fibres are used for preference, obtained by precipitationof an acid solution of collagen by adding NaCl, then washing and dryingthe precipitate obtained using aqueous solutions of acetone inconcentrations increasing from 80% to 100%.

A 30 g/l solution of collagen is prepared by dissolving it in 0.01 NHCl. Its volume is 49 liters. Periodic acid is added to it at a finalconcentration of 8 mM, i.e. 1.83 g/l. Oxidation takes place at anambient temperature close to 22° C. for 3 hours away from light.

Then an equal volume of a solution of sodium chloride is added to thesolution to obtain a final concentration of 41 g/l NaCl.

After waiting for 30 minutes, the precipitate is collected bydecantation through a fabric filter, with a porosity close to 100microns, then washed 4 times with a 41 g/l solution of NaCl in 0.01 NHCl. This produces 19 kg of acid saline precipitate. This washingprocess eliminates all traces of periodic acid or iodine derivativesduring oxidation of the collagen.

Then, several washes in an aqueous solution of 80% acetone are used toconcentrate the collagen precipitate and eliminate the salts present.

A final wash in 100% acetone is used to prepare 3.6 kg of a very denseacetone precipitate of acid, oxidized, non-reticulated collagen, with notrace of undesirable chemical products.

The acetone paste is diluted with apyrogenic distilled water at 40° C.,to obtain a 3% concentration of collagen, for a volume of 44 liters. Thecollagen suspension of a volume of 44 liters is heated for 30 minutes at50° C., then filtered under sterile conditions through a membrane of0.45 micron porosity in a drying oven at 40° C.

As soon as this solution is homogeneous and at 35° C., a sterileconcentrated solution of PEG 4000 (polyethylene glycol with a molecularweight of 4000 Daltons) and glycerine is added to it to produce a finalconcentration of 0.9% PEG, 0.54% glycerine and 2.7% oxidized collagen.

As soon as these additions have been made, the pH of the solution isadjusted to 7.0 by adding a concentrated solution of sodium hydroxide.

Preparation of a Multilayer Buttress Material

The collagen solution destined to form the non-porous layer, asdescribed in above, is poured in a thin layer on a flat hydrophobicsupport such as PVC or polystyrene, at an ambient temperature close to22° C. A continuous pocket, or channel, or a plurality of longitudinallyspaced pockets, or channels, are machined into the surface of thehydrophobic support. The pockets, or channels, in the support correspondto slots or openings in the anvil and/or staple cartridge. The number,dimension and spacial relationship of the pockets, or channels, aredetermined so as to provide a molded buttress which in turn provides areleasable pressure fit with the slots or openings provided in the anvilor staple cartridge when placed in cooperation therewith.

The porous layer, prepared as described above, is applied uniformly tothe solution of heated collagen, 5 to 20 minutes after it was pouredonto the support. This waiting time is the collagen solution gellingtime, required for application of the porous layer, to prevent itdissolving or becoming partially hydrated in the liquid collagen.

Penetration of the porous layer into the gelled collagen solution can beless than 0.5 mm.

The buttress material is then dehydrated in a jet of sterile air, atambient temperature, which leads to evaporation in about 18 hours.

The multilayer buttress material obtained is easy to remove from thesupport and can be cut to the dimensions required for the applicationconcerned, without weakening it.

The multilayer buttress material is then put into an airtight doublepolyethylene bag.

The unit is sterilized by gamma irradiation or electron beam (beta)irradiation at a dose of between 25 and 35 KGy.

The material is stable at ambient temperature.

EXAMPLE 2 Preparation of a Multilayer Buttress Material

The collagen solution destined to form the non-porous layer, asdescribed above in EXAMPLE 1, is poured in a thin layer equal to about0.106 g/cm² on a flat hydrophobic support such as PVC or polystyrene, atan ambient temperature close to 22° C. Several protrusions are machinedonto the surface of the mold. The protrusions on the mold correspond tothe pins located on the anvil and/or staple cartridge. The number,dimension and special relationship of the protrusions, are determined soas to provide a molded buttress which in turn provides a releasablepressure fit with the pins provided on the anvil or staple cartridgewhen placed in cooperation therewith.

The remaining collagen solution is diluted with ethyl alcohol and waterto produce a final concentration of 1.75% of oxidized collagen.

Using the diluted solution of 1.75% oxidized collagen, a second layerequal to about 0.041 g/cm² is poured over the first layer, 1 hour ormore after the spreading of the first layer.

Immediately, a surgical mesh reinforcement member is applied on thesecond layer of the diluted oxidized collagen. The reinforcement memberis a knitted isoelastic, multifilament polyglycolic acid mesh which maybe completely encapsulated by the second layer of oxidized collagen.

After 1 hour or more, the porous layer, prepared as described above inEXAMPLE 1, is applied to the mesh.

The multilayer, reinforced buttress material is dried in a dryingcabinet at about 20° C. and about 40% humidity with a horizontal airflow velocity of 1.2 m²/s. The air is blown from the right side of thecabinet to the left side of the cabinet and the incoming air is 0.2 μmfiltered and adjusted to 40% humidity. The duration of the drying cycleis between 12 and 24 hours.

EXAMPLE 3 Preparation of a Multilayer Buttress Material

The collagen solution destined to form the non-porous, as describedabove in EXAMPLE 1, is poured in a thin layer equal to about 0.106 g/cm²on a flat hydrophobic support such as PVC or polystyrene, at an ambienttemperature close to 22° C. The remaining collagen solution is dilutedwith ethyl alcohol and water to produce a final concentration of 1.75%of oxidized collagen.

Using the diluted solution of 1.75% oxidized collagen, a second layerequal to about 0.041 g/cm² is poured over the first layer, 1 hour ormore after the spreading of the first layer.

Immediately, a surgical mesh reinforcement member, is applied on thesecond layer of the diluted oxidized collagen. The reinforcement memberis a knitted isoelastic, multifilament polyglycolic acid mesh which maybe positioned on top of the second layer of oxidized collagen.

After 1 hour or more, the porous layer, prepared as described above inEXAMPLE 1, is applied to the mesh.

The multilayer, reinforced buttress material is dried in a dryingcabinet at about 20° C. and about 40% humidity with a horizontal airflow velocity of 1.2 m²/s. The air is blown from the right side of thecabinet to the left side of the cabinet and the incoming air is 0.2 μmfiltered and adjusted to 40% humidity. The duration of the drying cycleis between 12 and 24 hours.

The multilayer buttress of EXAMPLES 1-3 are applied to the staplecartridge and/or anvil of a surgical stapler, with the non-porous sidein contact with the surface of the cartridge and/or anvil. The edges ofa wound are approximated between the staple cartridge and the stapleanvil of the stapling apparatus. By firing the stapling apparatusstaples are forced out of the staple cartridge and through both themultilayer buttress and, the tissue. The staples are formed by contactwith the staple anvil. Once stapled in place the porous layeradvantageously reduces bleeding, assists in sealing the wound andallowing tissue ingrowth, if desired, while the non-porous layerprovides support for the porous layer and may assist in preventing theformation of adhesions. When present, as in EXAMPLES 2 and 3, thereinforcement member provides additional support to the multilayerbuttress and assist in preventing tears during stapling.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore, the above description shouldnot be construed as limiting, but merely as an exemplification ofpreferred embodiments. Those skilled in the art will envision othermodifications within the scope and spirit of the present disclosure.Such modifications and variations are intended to come within the scopeof the following claims.

What is claimed is:
 1. A surgical stapling apparatus comprising: astaple cartridge containing at least one staple; an anvil having astaple forming surface; and a buttress positioned adjacent the anvil orthe cartridge, the buttress comprising a non-porous layer disposedbetween first and second porous layers and a reinforcement memberpositioned within the non-porous layer, wherein pores of the porouslayers do not span across the entire thickness of the porous layers. 2.The surgical stapling apparatus of claim 1, wherein the non-porous layercomprises at least one material selected from the group consisting ofcollagen, gelatin, fibrin, fibrinogen, elastin, keratin, albumin,hydroxyethyl cellulose, cellulose, oxidized cellulose, hydroxypropylcellulose, carboxyethyl cellulose, carboxymethylcellulose, chitan,chitosan, alginate, poly(lactic acid), poly(glycolic acid),poly(hydroxybutyrate), poly (phosphazine), polyesters, polyethyleneglycols, polyalkyleneoxides, polyacrylamides,polyhydroxyethylmethylacrylate, polyvinylpyrrolidone, polyvinylalcohols, poly(caprolactone), poly(dioxanone), polyacrylic acid,polyacetate, polycaprolactone, polypropylene, aliphatic polyesters,glycerols, poly(amino acids), copoly(ether-esters), polyalkyleneoxalates, polyamides, poly(iminocarbonates), polyalkylene oxalates,polyoxaesters, polyorthoesters, polyphosphazenes and combinationsthereof.
 3. The surgical stapling apparatus of claim 1, wherein theporous layer comprises at least one material selected from the groupconsisting of poly(lactic acid), poly(glycolic acid),poly(hydroxybutyrate), poly(caprolactone), poly(dioxanone),polyalkyleneoxides, copoly(ether-esters), collagen, gelatin, thrombin,fibrin, fibrinogen, fibronectin, elastin, albumin, hemoglobin,ovalbumin, polysaccharides, hyaluronic acid, chondroitin sulfate,hydroxyethyl starch, hydroxyethyl cellulose, cellulose, oxidizedcellulose, hydroxypropyl cellulose, carboxyethyl cellulose,carboxymethyl cellulose, chitan, chitosan, agarose, maltose,maltodextrin, alginate, clotting factors, methacrylate, polyurethanes,cyanoacrylates, platelet agonists, vasoconstrictors, alum, calcium, RGDpeptides, proteins, protamine sulfate, epsilon amino caproic acid,ferric sulfate, ferric subsulfates, ferric chloride, zinc, zincchloride, aluminum chloride, aluminum sulfates, aluminum acetates,permanganates, tannins, bone wax, polyethylene glycols, fucans andcombinations thereof.
 4. The surgical stapling apparatus of claim 1,wherein the reinforcement member is a mesh.
 5. The surgical staplingapparatus of claim 1, wherein the reinforcement member is a suture. 6.The surgical stapling apparatus of claim 1, comprising a plurality ofreinforcement members oriented in at least one common direction.
 7. Thesurgical stapling apparatus of claim 1, wherein the reinforcement memberis encapsulated within the non-porous layer.
 8. The surgical staplingapparatus of claim 1, wherein a first reinforcement member isencapsulated within the non-porous layer and a second reinforcementlayer is encapsulated within the porous layer.
 9. The surgical staplingapparatus of claim 8, wherein the first reinforcement member comprises aplurality of reinforcement members oriented in a first direction withinthe non-porous layer and the second reinforcement layer comprises aplurality of reinforcement members oriented in a second direction withinthe porous layer.
 10. The surgical stapling apparatus of claim 1,wherein the pores of the porous layer are present on a central portionthereof.
 11. The surgical stapling apparatus of claim 1, wherein thebuttress further comprises a bioactive agent.
 12. The surgical staplingapparatus of claim 11, wherein the bioactive agent is combined with theporous layer.
 13. The surgical stapling apparatus of claim 11, whereinthe bioactive agent is combined with the non-porous layer.
 14. Thesurgical stapling apparatus of claim 11, wherein the bioactive agent iscombined with the reinforcement member.
 15. A surgical staplingapparatus comprising: a staple cartridge containing at least one staple;an anvil having a staple forming surface; and a buttress positionedadjacent the anvil or the cartridge, the buttress comprising anon-porous layer disposed between first and second porous layers, and areinforcement member positioned within the non-porous layer, wherein thereinforcement member comprises chopped fibers and wherein pores of theporous layers do not span across the entire thickness of the porouslayers.
 16. A method of sealing a wound comprising: enclosing tissuebetween a cartridge and an anvil of a surgical stapling apparatus, oneof the cartridge or anvil having a buttress positioned adjacent thereto,the buttress comprising a non-porous layer disposed between first andsecond porous layers having pores which do not span across the entirethickness of the porous layers, and a reinforcement member positionedwithin the non-porous layer; and ejecting staples from said cartridge tosecure the buttress to the tissue.